Performance of a large partial-depth guide wall to divert downstream migrating Atlantic salmon smolts at Tuilières dam, Dordogne River

Abstract

From 2010 to 2016, an evaluation of the performance of a partial-depth guide wall associated with three surface bypasses to ensure the safe downstream migration of Atlantic salmon smolts was conducted at the Tuilières power plant on the Dordogne River in southwestern France. The objectives of this study, during which 603 smolts were monitored using radio telemetry, were (i) to determine their escapement rate (passage through routes other than turbines), (ii) to analyse their behaviour faced with the structure and (iii) to assess the permeability of the guide wall as a function of turbine and spilling flows. The rate of escapement through the surface bypass routes varied from approximately 15% to 85%. The turbine flow was the main factor influencing the guide wall efficiency. The contribution of secondary bypasses, while significant for low flows, decreased rapidly with the increase in turbine flows. The vast majority of fish arrived on the two downstream bays of the wall or directly in the area of the main bypass, with the guiding effect of the guide wall becoming less noticeable with the increase of turbine flow. A modification of the depth of the guide wall in 2014 slightly improved its efficiency (by 5-10%) for low turbine flows. Logistic regression models were used to describe the evolution of the efficiency of the facilty as a function of the turbine flow and the probability of direct passage under a bay as a function of average velocity under this bay.Keywords: Atlantic salmon smolts / downstream migration / behaviour / hydroelectric plant / guide wall / radio-tracking Résumé -Efficacité d'un mur guideau de surface destiné à guider les smolts de saumon atlantique en migration de dévalaison au barrage de Tuilières sur la Dordogne. De 2010 à 2016 une évaluation des performances d'un mur guideau associé à des exutoires de surface visant à assurer la dévalaison sans dommage des smolts de saumon atlantique a été menée à la centrale hydroélectrique de Tuilières sur la rivière Dordogne dans le Sud-Ouest de la France. Cette étude, au cours de laquelle 603 smolts ont fait l'objet d'un suivi par radio télémétrie, avait pour objectifs i) d'évaluer les taux d'échappement (passages par d'autres voies que par les turbines) ii) d'analyser le comportement des smolts devant les ouvrages ainsi que (iii) l'évolution de la perméabilité du masque de guidage en fonction des conditions de débit turbiné et de débit déversé au barrage. Le taux d'échappement par les exutoires a varié de 15% à 85%. Le débit turbiné est le facteur principal influant sur l'efficacité du mur guideau. L'apport des exutoires secondaires, s'il est notable pour les faibles débits turbinés, diminue fortement avec l'augmentation de ces débits. Les poissons arrivent en grande majorité sur les travées aval du masque ou directement à proximité de l'exutoire principal, l'effet guidage du masque diminuant avec le débit turbiné. Une modification de la profondeur d'immersion du masque en 2014 n'améliore son efficacité (de 5 % à 10 %) que pour les faibles débits turb...

Improving bypass performance and passage success of Atlantic salmon smolts at an old fish-hostile hydroelectric power station: a challenging task

“…Haro et al (1998) observed that maintenance of positive rheotaxis and strong swimming behaviour along the bypass system were important factors in bypass effectiveness. Previous studies have already mentioned lower overall bypass passage minimum efficiency rates (5%-28%: Chanseau et al, 1999;Gosset and Travade, 1999;Fjeldstad et al, 2012;Larinier et al, 2020) and some similar efficiency to our study (32%, Croze, 2008;33%: Chanseau et al, 2002;37.1%: Bosc et al, 2016in Tomanova et al, 2018. However, the most recent studies have quantified best performance ranging from 55% to 100% (reviewed in Tomanova et al, 2018).…”

“…Hence, the results obtained in this study do not represent a complete vision of what would have happened during the entire migration season of smolts in the Amblève River, especially under more important flow conditions. Finally, we used hatchery smolts, but as observed by Karppinen et al (2014), Renardy et al (2020) and Larinier et al (2020), they remain highly sensitive to the environmental cues that trigger fish migration. However, Larocque et al (2020) observed differences in survival between wild and hatchery smolts (better for wild) during downstream migration in a Lake Ontario tributary.…”

“…Appropriate mitigation measures for turbine entrainment at hydroelectric power station has focused on the installation and operation of fish protection systems. In harmful hydroelectric stations, fish-friendly trash-racks as well as downstream bypasses have been developed and tested to prevent smolts from entering the turbines and to mitigate the negative effects of hydropower stations on migration (Coutant and Whitney, 2000;Larinier and Travade, 2002;Albayrak et al, 2018;Calles et al, 2012;Fjeldstad et al, 2018;Klopries et al, 2018;Tomanova et al, 2018;Tétard et al, 2019;Larinier et al, 2020;Renardy et al, 2020). Fish-friendly turbines (e.g.…”

Migration behaviour of Atlantic salmon smolts (Salmo salar L.) in a short and highly fragmented gravel‐bed river stretch

“…Ovidio et al (2017, Francis turbines) reported a research time of less than 1 h for the major proportion (70%) of the smolts. In large‐sized rivers, research time varied between 0.4 h (Larinier et al, 2020) and 4.7 h (Renardy et al, 2021) at hydropower stations equipped with Kaplan turbines. In our study, after choosing a migration route, the required median crossing time varied between 0.5 h and 2.4 h. The crossing speed was higher after passage over spillway gates than through Francis turbines or Archimedes screws.…”

Evaluation of a fine-spaced angled rack with surface bypass in providing safe and timely downstream passage for salmon smolts and silver eels

“…Several other reasons, linked to bypass location and hydraulic conditions on the rack may, however, also explain this poorer performance. Firstly, with an angled rack, fish are guided toward the downstream end, where a full-depth bypass entrance should ideally be positioned (Courret and Larinier, 2008;Larinier et al, 2020). However, structural factors at the Pébernat intake led to a suboptimal bypass position (approximately 6 m downstream from the rack end), and design (a wide but shallow entrance), perhaps making the bypass less attractive.…”